Abstract
It has been discussed concerning a computer simulation method of sound transmission in a room(M. R. Schroeder and B. S. Atal, IEEE Intern. Conv. Rec. , 150-155(1963)). This paper presents a basic conception(Fig. 1, Eq. (1))and an approaching method(Eq. (2))for acoustic design of room by computer simulation and hearing tests of the simulated sound. Based on the "Ray Theory", the sound reflection from boundaries such as walls and ceilings etc. are simulated by using the measured transfer functions. One of the methods of measuring the transfer function of the walls has been treated in previous papers as a function of the angle of incidence including uneven walls(Y. Ando. J. Inst. Electron. Comm. Engineers, Japan, 51-A, 10-18(1968)and Y. Ando, Y. Suzumura and Z. Maekawa, J. Acoust. Soc. Japan, 28, 289-298(1972)). Also, the measured acoustic centers of a human ear are demonstrated in Fig. 8 to simulate their localization. The acoustic centers correspond to the phase of the transfer function(Eq. (12))by the sound diffraction around the listener's head including the lobes, and may be regarded as a receiving point of ears. The reflecting sound waves were simulated by making the convolution of the impulse response of the wall with an encoded reverberation-free speech signals. The simulated speech signals were judged in an anechoic chamber as a function of the angle of incidence of the signal to the walls(Table 1(a), (b)). Effective duration of the impulse response of the walls is about 2. 0 msec. Some of the sampled signals of the impulse response can be ignored for convolution calculations if their absolute values are smaller than a small value ε(Fig. 12), because of their very small contributions to the output signals. This may be seen as one of the windows on the impulse response for saving the computation time. Finally, many problems arising during the investigation are pointed out.
